Method for forming an insert injection-molded article exhibiting improved resistance to heat shock utilizing a specifically defined polybutylene terephthalate composition

ABSTRACT

The present invention provides a polybutylene terephthalate resin composition, having performance of high durability and the like in a cold cycle environment, and having high strength. Specifically, relative to 100 parts by weight of a polybutylene terephthalate resin (A) having 30 meq/kg or less of the amount of terminal carboxyl groups, there are added a carbodiimide compound (B) in an amount of 0.3 to 1.5 equivalents of the carbodiimide functional group when the amount of carboxyl terminal group in the polybutylene terephthalate resin (A) is set as 1, 20 to 100 parts by weight of a fibrous filler (C), and 5 to 15 parts by weight of an elastomer (D).

TECHNICAL FIELD

The present invention relates to a polybutylene terephthalate resincomposition and a molded article thereof which are excellent in highstrength and resistance to heat shock.

BACKGROUND ART

Polybutylene terephthalte resins are used as engineering plastics inwide fields including automobile parts, electric and electronic parts,or the like owing to their excellent mechanical properties, electricproperties, and other physical and chemical properties, and their goodworkability. In particular, since their heat resistance and strength canbe increased by adding a fibrous filler such as glass fiber thereto,polybutylene terephthalte resins are often used by reinforcing thereofby the fibrous filler.

Specifically in the automobile field, polybutylene terephthalate isoften used as the material of sensor for electric control and of ECUhousing. In that case, for the parts (insert molded articles) beingmounted in an environment of severe temperature increase/decrease, suchas engine room of automobile, the toughness of the parts is oftenimproved by adopting an elastomer and the like to prevent crackgeneration caused by strain resulting from the difference in linearexpansion between metal and resin. Many kinds of compositions have beenproposed for that purpose.

For example, JP-A 3-285945 discloses the improvement in the resistanceto heat shock by adding an elastomer such as ethylene-alkyl acrylate topolybutylene terephthalate. The resin, however, does not exhibitsatisfactory resistance to heat shock and does not exhibit satisfactoryresistance to hot water, although the improvement effect of thoseresistances is recognized in comparison with that of non-additive resin.

JP-A 60-210659 discloses the improvement of the resistance to hot waterby adding an elastomer such as ethylene-alkyl acrylate and carbodiimideto polybutylene terephthalate. That kind of composition, however, doesnot exhibit satisfactory resistance to heat shock, although theresistance to hot water is improved.

Furthermore, JP-A 2001-234046 discloses that a resin compositioncomposed of polybutylene terephthalate, a material providing impactresistance, and an aromatic polyvalent carboxylic acid ester compoundexhibits excellent resistance to heat shock. However, the addition ofthe aromatic polyvalent carboxylic acid ester compound raises a problemof deteriorating the strength and the toughness, and also raises aproblem of inducing bleeding at high temperatures.

As described above, although the addition of elastomer in order toimprove the toughness is known, the addition thereof at an amountnecessary for improving the toughness raises a problem of deterioratingthe strength.

DISCLOSURE OF THE INVENTION

The present invention has been made to solve the above technicalproblems, and an object of the present invention is to provide apolybutylene terephthalate resin composition having performance of highdurability and the like in cold cycle environment, and further havinghigh strength, and to provide a molded article thereof.

The inventors of the present invention have conducted detail studies toobtain a polybutylene terephthalate resin composition capable ofachieving the above object, and have found that a composition which ismade up mainly of a polybutylene terephthalate resin having 30 meq/kg orless of terminal carboxyl groups and to which a specific amount of acarbodiimide compound, a fibrous filler, and an elastomer are added incombination gives extremely high resistance to heat shock and resistanceto hydrolysis without significant deterioration in the mechanicalproperties, thus having completed the present invention.

That is, the present invention provides a polybutylene terephthalateresin composition, obtained by blending 100 parts by weight of apolybutylene terephthalate resin (A) having 30 meq/kg or less ofterminal carboxyl groups with a carbodiimide compound (B) in an amountof 0.3 to 1.5 equivalents of the carbodiimide functional group when theamount of terminal carboxyl groups in the polybutylene terephthalateresin (A) is set as 1; 20 to 100 parts by weight of a fibrous filler(C), and 5 to 15 parts by weight of an elastomer (D), and provides amolded article obtained by molding the resin composition, specificallyan insert-molded article thereof.

The present invention also provides a polybutylene terephthalate resincomposition including: 100 parts by weight of a polybutyleneterephthalate resin (A) having 30 meq/kg or less of terminal carboxylgroups; a carbodiimide compound (B) in an amount of 0.3 to 1.5equivalents of the carbodiimide functional group when the amount ofterminal carboxyl groups in the polybutylene terephthalate resin (A) isset as 1; 20 to 100 parts by weight of a fibrous filler (C); and 5 to 15parts by weight of an elastomer (D).

The present invention further provides an insert-molded article composedof a resin material of the above polybutylene terephthalate resincomposition.

The present invention further provides a method of manufacturing theabove polybutylene terephthalate resin composition, including blending100 parts by weight of a polybutylene terephthalate resin (A) having 30meq/kg or less of terminal carboxyl groups with a carbodiimide compound(B) in an amount of 0.3 to 1.5 equivalents of the carbodiimidefunctional group, when the amount of terminal carboxyl groups in thepolybutylene terephthalate resin (A) is set as 1; 20 to 100 parts byweight of a fibrous filler (C); and 5 to 15 parts by weight of anelastomer (D).

The present invention further provides a method of manufacturing amolded article or an insert-molded article containing the step ofperforming injection-molding of the above polybutylene terephthalateresin composition having 120 MPa or higher tensile strength inaccordance with ISO 527.

The present invention provides a polybutylene terephthalate resincomposition having excellent performance of high durability and the likein a cold cycle environment and having excellent resistance tohydrolysis. The polybutylene terephthalate resin composition of thepresent invention is useful as varieties of molded articles,specifically as insert-molded articles.

DETAILED DESCRIPTION OF THE INVENTION

The structural components of the resin material of the present inventionwill be described in detail in the following. The (A) polybutyleneterephthalate resin which is the basic resin of the resin composition ofthe present invention is a polybutylene terephthalate-based resin whichis obtained by polycondensation of a dicarboxylic acid componentcontaining at least terephthalic acid or an ester-forming derivativethereof (such as lower alcohol ester) and a glycol component containingat least a C4 alkylene glycol (1,4-butane diol) or an ester-formingderivative thereof. The polybutylene terephthalate resin is not limitedto the homo-polybutylene terephthalate resin, and may be a copolymercontaining 60% by mole or more, specifically about 75 to 95% by mole, ofbutylene terephthalate unit.

The polybutylene terephthalate resin in the present invention isproduced by dissolving a crushed polybutylene terephthalate sample inbenzyl alcohol for 10 minutes at 215° C., followed by titrating thesolution by using an aqueous solution of 0.01N sodium hydroxide tothereby be used as the polybutylene terephthalate resin having 30 meq/kgor less of the amount of terminal carboxyl groups measured, preferably25 meq/kg or less thereof.

The use of a polybutylene terephthalate resin having more than 30 meq/kgof the amount of terminal carboxyl groups deteriorates the effect ofimproving the resistance to heat shock even by controlling the amount tobe added of carbodiimide compound, and increases the lowering of thestrength by hydrolysis in a moist-heat environment.

The lower limit of the amount of terminal carboxyl groups is notspecifically limited. However, the polybutylene terephthalate resinhaving less than 5 meq/kg of the amount of terminal carboxyl groups isgenerally difficult to be produced, and the resin having less than 5meq/kg thereof does not allow the reaction with carbodiimide compound toproceed sufficiently, which may result in insufficient effect ofimproving the resistance to heat shock. Accordingly, the amount ofterminal carboxyl groups in the polybutylene terephthalate resin ispreferably 5 meq/kg or more, and specifically preferably 10 meq/kg ormore.

Furthermore, the intrinsic viscosity (IV) of the applied (A)polybutylene terephthalic resin is preferably within the range of 0.67to 0.90 dL/g. If the intrinsic viscosity exceeds 0.90 dL/g, theflowability at the time of molding necessary for the insert-moldingarticle cannot be attained in some cases. The intrinsic viscosity of0.90 dL/g or less can also be attained by blending polybutyleneterephthalate resins having different intrinsic viscosities from eachother, for example, the one having an intrinsic viscosity of 1.00 dL/gand the one having an intrinsic viscosity of 0.70 dL/g. The intrinsicviscosity can be determined, for example, in o-chlorophenol at 35° C.

In the polybutylene terephthalate resin, examples of the dicarboxylicacid component (comonomer component) other than terephthalic acid and anester-forming derivative thereof are: an aromatic dicarboxylic acidcomponent (such as C₆-C₁₂ aryldicarboxylic acid including isophthalicacid, phthalic acid, naphthalene dicarboxylic acid or diphenyl etherdicarboxylic acid); an aliphatic dicarboxylic acid component (such asC₄-C₁₆ alkyldicarboxylic acid including succinic acid, adipic acid,azelaic acid, and sebacic acid, and C₅-C₁₀ cycloalkyl dicarboxylic acidincluding cyclohexane dicarboxylic acid); and an ester-formingderivative thereof. Those dicarboxylic acid components can be used aloneor in combination of two or more thereof.

Preferable dicarboxylic acid component (comonomer component) includes anaromatic dicarboxylic acid component (specifically C₆-C₁₀ aryldicarboxylic acid such as isophthalic acid) and an aliphaticdicarboxylic acid component (specifically C₆-C₁₂ alkyl dicarboxylic acidsuch as adipic acid, azelaic acid, and sebacic acid).

Examples of glycol component (comonomer component) other than 1,4-butanediol are: an aliphatic diol component (such as alkylene glycol(including C₂-C₁₀ alkylene glycol such as ethylene glycol, propyleneglycol, trimethylene glycol, 1,3-butylene glycol, hexamethylene glycol,neopenthyl glycol, and 1,3-octane diol, or polyoxy C₂-C₄ alkylene glycolsuch as diethylene glycol, triethylene glycol or dipropylene glycol),and alicyclic diol such as cyclohexane dimethanol or hydrogenatedbisphenol A); an aromatic diol component (such as aromatic alcoholincluding bisphenol A and 4,4-dihydroxybiphenyl, and C₂-C₄ alkyleneoxideadduct of bisphenol A (for example, 2-mole adduct of ethylene oxide ofbisphenol A and 3-mole adduct of propylene oxide of bisphenol A)); andan ester-forming derivative thereof. These glycol components can also beused alone or in combination of two or more thereof.

Preferred glycol component (Comonomer component) includes an aliphaticdiol component (specifically C₂-C₆ alkylene glycol, polyoxy C₂-C₃alkylene glycol such as diethylene glycol, and alicyclic diol such ascyclohexane dimethanol).

Any of the polybutylene terephthalate-based polymers obtained bypolycondensation of above compounds as the monomer components can beused as the (A) component of the present invention. The combined use ofhomo-polybutylene terephthalate polymer and polybutylene terephthalatecopolymer is also useful.

The (B) carbodiimide compound used in the present invention is acompound having carbodiimide group (—N═C═N—) in the molecule. Applicablecarbodiimide compound includes an aliphatic carbodiimide compound havingthe aliphatic main chain, an alicyclic carbodiimide compound having thealicyclic main chain, and an aromatic carbodiimide compound having thearomatic main chain, and a preferred one is an aromatic carbodiimidecompound in terms of resistance to hydrolysis.

Examples of the aliphatic carbodiimide compound include diisopropylcarbodiimide, dioctyldecyl carbodiimide, or the like. An example of thealicyclic carbodiimide compound includes dicyclohexyl carbodiimide, orthe like.

Examples of aromatic carbodiimide compound include: a mono- ordi-carbodiimide compound such as diphenyl carbodiimide,di-2,6-dimethylphenyl carbodiimide, N-tolyl-N′-phenyl carbodiimide,di-p-nitrophenylcarbodiimide, di-p-aminophenyl carbodiimide,di-p-hydroxyphenyl carbodiimide, di-p-chlorophenyl carbodiimide,di-p-methoxyphenyl carbodiimide, di-3,4-dichlorophenyl carbodiimide,di-2,5-dichlorophenyl carbodiimide, di-o-chlorophenyl carbodiimide,p-phenylene-bis-di-o-tolyl carbodiimide, p-phenylene-bis-dicyclohexylcarbodiimide, p-phenylene-bis-di-p-chlorophenyl carbodiimide orethylene-bis-diphenyl carbodiimide; and a polycarbodiimide compound suchas poly(4,4′-diphenylmethane carbodiimide),poly(3,5′-dimethyl-4,4′-biphenylmethane carbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylene carbodiimide),poly(3,5′-dimethyl-4,4′-diphenylmethane carbodiimide), poly(naphthylenecarbodiimide), poly(1,3-diisopropylphenylene carbodiimide),poly(1-methyl-3,5-diisopropylphenylene carbodiimide),poly(1,3,5-triethylphenylene carbodiimide), andpoly(triisopropylphenylene carbodiimide). These compounds can be used incombination of two or more of them. Among these, specifically preferredones to be used are di-2,6-dimethylphenyl carbodiimide,poly(4,4′-diphenylmethane carbodiimide), poly(phenylene carbodiimide),and poly(triisopropylphenylene carbodiimide).

A preferred (B) carbodiimide compound to be used is the one having 2000or larger molecular weight. The one having a molecular weight of lessthan 2000 may generate gas and odor when the retention time is longduring melt-kneading and during molding.

The blending amount of (B) carbodiimide compound corresponds to theamount of carbodiimide functional group within the range of 0.3 to 1.5equivalents when the amount of the terminal carboxyl groups in the (A)polybutylene terephthalate resin is set as 1.

If the amount of (B) component is excessively small, the effect ofimproving the resistance to heat shock, which is an object of thepresent invention, cannot be attained. If the amount thereof isexcessively large, there likely appears the lowering of flowability andthe generation of gel component and carbide at the time of compoundingand molding processing, and appear the deterioration of mechanicalcharacteristics such as tensile strength and flexural strength, and therapid decrease in strength in a moist heat environment. This is becauseof the deterioration of adhesion between the polybutylene terephthalateresin and the glass fiber caused by the (B) component. A preferredblending amount of the (B) component corresponds to the amount ofcarbodiimide functional group within the range of 0.5 to 1.5equivalents, and more preferably 0.8 to 1.2 equivalents.

Examples of the (C) fibrous filler used in the present invention includeglass fiber, carbon fiber, potassium titanate fiber, silica-aluminafiber, zirconia fiber, metal fiber, organic fiber, or the like. Amongthese, glass fiber is preferred.

For the glass fiber, any of known glass fibers is preferably usedirrespective of the fiber diameter, the shape such as cylinder, cocoon,or elliptical cross section of the glass fiber, and the length of andthe cutting method in manufacturing chopped strand, roving, or the like.Although the present invention is independent of the kind of glass,preferred ones are E-glass and corrosion-resistant glass containingzirconium element in the composition in view of the quality.

According to the present invention, in order to improve thecharacteristic of interface between the fibrous filler and the resinmatrix, a fibrous filler surface-treated by using an organic treatmentagent such as amino-silane compound and epoxy compound is specificallypreferred, and a glass fiber containing 1% by weight or more of organictreatment agent, expressed by the loss on heating, is specificallypreferred. Preferable amino-silane compound and epoxy compound used inthose fibrous fillers are any of known ones, irrespective of the kind ofamino-silane and epoxy compound used for the surface treatment of thefibrous filler according to the present invention.

The amount of (C) fibrous filler to be used is 20 to 100 parts by weightrelative to 100 parts by weight of the (A) polybutylene terephthalateresin. If the amount of (C) fibrous filler is smaller than the aboverange, the variations in linear expansion accompanied with the coldcycle become large, which is not preferable in view of resistance toheat shock. If the amount of (C) fibrous filler to be used exceeds theabove range, the allowable strain of the material decreases, which isunfavorable from the point of resistance to heat shock. The amount of(C) fibrous filler is preferably within the range of 20 to 80 parts byweight, and more preferably 30 to 60 parts by weight.

Meanwhile, the present invention allows the combined blending of anon-fibrous filler which has no fibrous shape as in the case of the (C)component, that is to say, an inorganic filler in plate shape orgranular shape, or a mixture thereof. Such non-fibrous filler includesglass flake, glass bead, mica, talc, carbon black, calcium carbonate, orthe like.

The (D) elastomer used in the present invention is preferably athermoplastic elastomer or a core-shell elastomer. The thermoplasticelastomer includes a grafted olefin-based elastomer, a graftedstyrene-based elastomer, and a grafted polyester-based elastomer.

The addition amount of the (D) elastomer is within the range of 5 to 15parts by weight relative to 100 parts by weight of the (A) polybutyleneterephthalate resin, and preferably 5 to 10 parts by weight. If theaddition amount of the (D) elastomer is less than 5 parts by weight, theeffect of improving the resistance to heat shock cannot be attained. Ifthe addition amount thereof exceeds 15 parts by weight, the strengthdecreases.

A preferable grafted olefin-based elastomer is a copolymer composedmainly of ethylene and/or propylene, and there is preferably applicablea graft-copolymer chemically bonded by branching or cross-linking one ormore of: (a-1) a copolymer of ethylene-unsaturated carboxylic acid alkylester or (a-2) an olefin-based copolymer composed of α-olefin andglycidyl ester of α,β-unsaturated acid; and (b) a polymer or copolymerconstituted mainly by repeated units represented by the formula (1).

where, R is hydrogen or a lower alkyl group, and X is one, two or moregroup selected from —COOCH₃, —COOC₂H₅, —COOC₄H₉, —COOCH₂CH(C₂H₅)C₄H₉,—C₆H₅, and —CN.

Such graft-copolymer specifically produces the improvement effect ofresistance to heat shock.

Examples of the (a-1) ethylene-unsaturated carboxylic acid alkyl estercopolymer include random copolymers such as ethylene-acrylic acidcopolymer, ethylene-methacrylic acid copolymer, ethylene-acrylicacid-ethyl acrylate copolymer, ethylene-acrylic acid-ethyl acrylatecopolymer, ethylene-vinyl acrylate copolymer, and ethylene-vinylacetate-ethyl acrylate copolymer. These copolymers can be mixed for use.Furthermore, the α-olefin as one of the monomers structuring theolefin-based copolymer of (a-2) includes ethylene, propylene, andbutene-1, and ethylene is preferably used. Moreover, the glycidyl esterof α,β-unsaturated acid as another monomer structuring (a-2) is acompound represented by the general formula (2), including acrylic acidglycidyl ester, methacrylic acid glycidyl ester, and ethacrylic acidglycidyl ester. Specifically, methacrylic acid glycidyl ester ispreferably used.

where, R₁ is hydrogen atom or lower alkyl group.

The olefin-based copolymer composed of α-olefin (such as ethylene) andglycidyl ester of α,β-unsaturated acid can be obtained bycopolymerization through a known radical polymerization reaction. Theratio of the α-olefin to the glycidyl ester of α,β-unsaturated acid ispreferably 70 to 99% by weight of the α-olefin to 1 to 30% by weight ofthe glycidyl ester of α,β-unsaturated acid.

The polymer or copolymer (b) which is graft-polymerized with theolefin-based copolymer (a-1) or (a-2) is a copolymer composed of asingle polymer or two or more polymers constituted by a repeated singleunit represented by the general formula (1), such aspolymethylmethacylate, polyethylacrylate, polybutylacrylate,poly(2-ethylhexylacrylate), polystyrene, polyacrylonitrile,acrylonitrile-styrene copolymer, butylacrylate-methylmethacrylatecopolymer or butylacrylate-styrene copolymer. Specifically preferred oneis butylacrylate-methylmethacrylate copolymer. Also these polymers andcopolymers (b) are prepared by radical polymerization of correspondingvinyl-based monomers.

The graft copolymer preferably used in the present invention is not asingle use of the olefin-based copolymer of (a-1) or (a-2) or of the(co)polymer of (b), but has the features as a graft copolymer having abranched or cross-linked structure in which the copolymer of (a-1) or(a-2) and the (co)polymer of (b) are chemically bonded at least at oneposition of the molecular structure. With such a graft structure, therecan be attained a significant effect which cannot be obtained by a solecomposition of (a-1), (a-2), or (b). The ratio of (a-1) or (a-2) to (b)to constitute the graft copolymer is within the range of 95:5 to 5:95(weight ratio), preferably 80:20 to 20:80.

The styrene-based elastomer includes a block or graft copolymer (orhydrogenated compound thereof) composed of: the hard segment constitutedby a polymer or copolymer of aromatic vinyl monomer such as styrene,α-methylstyrene, or vinyltoluene; and the soft segment constituted by apolymer or copolymer of at least one monomer selected from α-olefin(including α-C₂-C₁₂ olefin such as ethylene, propylene, 1-butene,1-hexene, or 1-octene), and diene-based monomer (such as butadiene orisoprene).

The styrene-based elastomer may be an acid-modified elastomer obtainedby being modified with acid or acid anhydride such as (meth)acrylic acidor maleic anhydride, a copolymerizable monomer having glycidyl group orepoxy group, (such as glycidyl(meth)acrylate), and an elastomer havingreactive functional group, such as epoxy-modified elastomer obtained byepoxidizing the unsaturated bond of the elastomer.

Examples of typical styrene-based elastomers can include: astyrene-diene-styrene block copolymer (styrene-butadiene-styrene blockcopolymer (SBBS), and styrene-isoprene-styrene block copolymer (SIS)); ahydrogenated block copolymer (styrene-ethylene butylene-styrene blockcopolymer (or hydrogenated (styrene-butadiene-styrene block copolymer))(SEBS), styrene-ethylene propylene-styrene block copolymer (orhydrogenated (styrene-isoprene-styrene block copolymer)) (SEPS),styrene-ethylene ethylene propylene-styrene block copolymer (SEEPS), andhydrogenated polymer of random styrene-butadiene copolymer); and amodified copolymer prepared by introducing a functional group (such asepoxy group, carboxyl groups or acid anhydride group) to thesecopolymers (epoxylated styrene-diene copolymer in which the unsaturatedbond of diene is epoxylated, (such as epoxylated styrene-diene-styreneblock copolymer and a hydrogenated polymer thereof)).

Next, the core-shell elastomer is a polymer having multilayer structurecomposed of a core layer (core part) and a shell layer which covers aportion or all of the core layer (surface of the core layer). Thecore-shell elastomer preferably has the core layer made of a rubbercomponent (soft component), specifically made of an acrylic-basedrubber. The glass transition temperature of the rubber component is, forexample, less than 0° C. (−10° C. or less, for example), preferably −20°C. or less (about −180° C. to −25° C., for example), and more preferablymay be −30° C. or less (about −150° C. to −40° C., for example).

The acrylic-based rubber as the rubber component is a polymer composedmainly of an acrylic monomer (specifically acrylic acid ester such asalkylacrylate (acrylic acid C₁-C₁₂ alkyl ester such as butyl acrylate,preferably acrylic acid C₁-C₈ alkyl ester, more preferably acrylic acidC₂-C₆ alkyl ester)). The acrylic-based rubber may be a polymer orcopolymer of acrylic-based monomer, (copolymer of acrylic-basedmonomers, copolymer of acrylic-based monomer with another monomercontaining unsaturated bond, and the like), and may be a copolymer ofacrylic-based monomer (and another monomer containing unsaturated bond)with cross-linking monomer.

The shell layer of the core-shell elastomer adopts a vinyl-basedpolymer. The vinyl-based polymer is obtained by polymerization orcopolymerization of at least one monomer selected from aromatic vinylmonomer, cyanated vinyl monomer, methacrylic acid ester-based monomer,and acrylic acid ester monomer. The rubber layer and the shell layer ofsuch a core-shell type copolymer are normally bonded together by graftcopolymerization. The graft copolymerization is attained, as needed, byadding a graft-crossing agent which reacts with the shell layer at thetime of polymerization of the rubber layer, thus providing the rubberlayer with the reactive group, followed by forming the shell layer.

The polyester-based elastomer can be grouped into polyether type andpolyester type. Any of them can be used if only the flexural modulus is1000 MPa or less, preferably 700 MPa or less. If the flexural modulusexceeds 1000 MPa, sufficient flexibility cannot be attained. Thepolyether type polyester-based elastomer is a polyester elastomercomposed of an aromatic polyester as the hard segment, and a polyesteras the soft segment made of an oxy-alkylene glycol polymer anddicarboxylic acid. The aromatic polyester unit in the hard segment is apolycondensate of dicarboxylic acid compound with dihydroxy compound, apolycondensate of oxycarboxylic acid compound, or a polycondensate ofthese three components. For example, polybutylene terephthalate and thelike are used as the hard segment. The soft segment to be used includesa compound obtained by polycondensation of polyalkylene ether withdicarboxylic acid. For example, an esterified compound of polyoxytetramethylene glycol, derived from tetrahydrofuran is used. The abovepolyether elastomer is commercially available as: PELPRENE P-30B, P-70B,P-90B, and P-280B, manufactured by Toyobo Co., Ltd.; Hytrel 4057, 4767,6347, and 7247, manufactured by Du Pont-Toray Co., Ltd.; Riteflex 655manufactured by Ticona LLC; or the like.

The polyester type elastomer is a polyester elastomer composed of anaromatic polyester as the hard segment and an amorphous polyester as thesoft segment. The aromatic polyester unit in the hard segment is thesame to that of the above polyether type elastomer. The soft segment isa ring-opening polymer of lactone, that is to say, a polylactone, or analiphatic polyester derived from aliphatic dicarboxylic acid andaliphatic diol. The polyester type elastomer is commercially availableas PELPRENE S-1002 and S-2002, manufactured by Toyobo Co., Ltd., or thelike.

In order to further impart a desired characteristic depending on theobject, the composition of the present invention can contain knownsubstances which are commonly added to thermoplastic resins andthermosetting resins, such as stabilizer including antioxidant,heat-stabilizer, or UV absorber, antistatic agent, coloring agent suchas dye or pigment, lubricant, plasticizer, crystallization accelerator,crystal nucleating agent, and epoxy compound within the range notdeteriorating the effect of the present invention.

In particular, although antistatic agent, coloring agent, lubricant, andplasticizer often contain carboxyl groups, hydroxyl group, and aminogroup, these functional groups are preferably not contained because theylikely react with carbodiimide group.

In the present invention, in order to improve the moldability, a moldreleasing agent can be added. Any type of mold releasing agent can bepreferably applied, including olefin-based polymer, aliphatic amidecompound, and aliphatic ester compound. Specifically preferred moldreleasing agent is an olefin-based polymer presumed to have lowreactivity with carbodiimide compound, or an aliphatic ester compoundhaving 100 or less of hydroxyl group value determined by the Japan OilChemists' Society Method 2, 4, 9, 2-71 (Pyridine-acetic anhydridemethod).

Additive containing carboxyl groups, hydroxyl group, or amino group ispreferably not used.

The resin composition to be used in the present invention can be easilyprepared by facilities and method commonly used as the conventionalresin composition preparation method. Examples are: (1) the method inwhich the respective components are mixed together, and the mixture iskneaded in and extruded from a single screw or twin screw extruder toform pellets, followed by molding; (2) the method in which pelletshaving different compositions from each other are prepared, andspecified amounts of the respective pellets are mixed together to besubjected to molding, and then the molded article having a desiredcomposition is obtained; and (3) the method in which one or morecomponents are directly supplied to the molding machine. Any ofabove-given methods can be applied. The method in which a portion of aresin component is prepared in fine powder form, which is then mixedwith other components, is a preferred one to attain homogeneous blendingof the components.

In preparing pellets kneaded by using an extruder, the temperature ofcylinder of the extruder is preferably set so that the temperature ofresin in the extruder is within the range of 240° C. to 300° C., andmore preferably 250° C. to 270° C. If the temperature thereof is below240° C., the reaction between polybutylene terephthalate andcarbodiimide becomes insufficient, and thus, resistance to hydrolysisand resistance to heat-shock may be insufficient, or excessively highviscosity of molten material may result in breaking fibrous filler,which may finally lead to failing to attain necessary mechanicalproperties. When the temperature of the resin exceeds 300° C., the resindecomposition likely occurs, and the resistance to hydrolysis and theresistance to heat shock may become insufficient.

In the same way as in molding, it is preferable to set the temperatureof cylinder of the extruder so that the resin temperature in the moldingmachine is within the range of 240° C. to 300° C., and more preferably250° C. to 270° C. Outside that temperature range, insufficientproperties may result in the same way as in the above case. The moldtemperature at the time of injection molding is preferably within therange of 40° C. to 100° C., more preferably 60° C. to 90° C. If the moldtemperature is below 40° C., the post-shrinkage occurs and strain isgenerated to thereby fail in attaining a desired shape or to fail inattaining sufficient resistance to heat shock. If the mold temperatureexceeds 100° C., the molding cycle takes a long time, which deterioratesthe mass-production performance.

Furthermore, the (B) carbodiimide compound can be blended as the masterbatch made up of a resin as the matrix, and the use of master batch isoften easy in terms of practical handling. A master batch ofpolybutylene terephthalate resin is preferably used. However, a masterbatch prepared by other resins may also be applicable. In the case ofmaster batch of polybutylene terephthalate resin, the amount of themaster batch may be adjusted so as to assure the range of specifiedblending amount of the (B) carbodiimide compound. The master batch maybe preliminarily added at the time of melting and kneading to formhomogeneous pellets. Alternatively, components other than thecarbodiimide compound are preliminarily formed as homogeneous pellets bymelt-kneading and the like, and the pellet-blend, in which the masterbatch pellets of the carbodiimide compound are dry-blended at the timeof molding, may be used for molding.

The resin composition of the present invention can be set as 300 Pa·s orless of the melt viscosity at a temperature of 260° C. and a shear rateof 1000 sec⁻¹ in accordance with ISO 11443. Furthermore, the meltviscosity can also be set as 250 Pa·s or less. Unless the melt viscositysecures 300 Pa·s or less, the flowability becomes insufficient, and theresin may not be filled in the mold in some cases.

The resin composition of the present invention can achieve the tensilestrength of 120 MPa or more, specifically 130 MPa or more in accordancewith ISO 527.

The polybutylene terephthalate resin composition according to thepresent invention is particularly useful for varieties ofinsert-injection molded articles.

EXAMPLES

The present invention is described below in more detail referring to thefollowing Examples. However, the present invention is not limited tothese examples.

Examples 1 to 5, Comparative Examples 1 to 4

The respective components given in Table 1 were weighed and weredry-blended together. The blend was then melt-kneaded in a 30 mm dia.twin screw extruder (TEX-30, manufactured by The Japan Steel Works,Ltd.) at a cylinder temperature of 260° C., an extrusion rate of 15kg/h, and a screw rotational speed of 150 rpm, to form pellets. By usingthe pellets prepared, respective test pieces were formed to measurevarious physical properties. The results are summarized in Table 1.

The detail of the components used and the measurement method forevaluating the physical properties are given below.

(A) Polybutylene Terephthalate Resin

-   -   (A-1) Manufactured by WinTech Polymer Ltd.; intrinsic viscosity        of 0.69, and amount of terminal carboxyl groups of 24 meq/kg    -   (A-2) Manufactured by WinTech Polymer Ltd.; intrinsic viscosity        of 0.70, and amount of terminal carboxyl groups of 44 meq/kg

(B) Carbodiimide Compound

-   -   (B-1) Aromatic carbodiimide compound: Stabaxol P, manufactured        by Rhein Chemie Japan Ltd.    -   (B-2) Aromatic carbodiimide compound: Stabaxol P400,        manufactured by Rhein Chemie Japan Ltd.

(C) Glass Fiber

-   -   (C-1) ECS03-T127, manufactured by Nippon Electric Glass Co.,        Ltd.

(D) Elastomer

-   -   (D-1) MODIPER A5300 (ethylene ethyl        acrylate-graft-butylacrylate/methylmethacrylate), manufactured        by NOF Corporation    -   (D-2) SEPTON 4055 (polystyrene-poly(ethylene-ethylene/propylene)        block polystyrene copolymer), manufactured by Kuraray Co., Ltd.    -   (D-3) EXL 5136, acrylic-based core-shell polymer, manufactured        by Rohm and Haas Company    -   (D-4) PERPREN P90BD (polyester-based elastomer), manufactured by        Toyobo Co., Ltd.

[Melt Viscosity Characteristic]

The melt viscosity was measured in accordance with ISO 11443 under thecondition of a cylinder temperature of 260° C. and a shear rate of 1000sec⁻¹.

[Resistance to Heat Shock]

Pellets to be used were molded into an insert-molded article byinsert-injection molding under the condition of a resin temperature of260° C., a mold temperature of 65° C., an injection time of 25 sec, anda cooling time of 10 sec by using a mold for forming test piece (a moldinserting an iron core of 18 mm in length, 18 mm in width, and 30 mm inheight into a rectangular cylinder of 22 mm in length, 22 mm in width,and 51 mm in height) so that the minimum thickness of a portion of resinsection becomes 1 mm. The insert molded article obtained was subjectedto heat shock resistance testing in which one cycle includes heating at140° C. for one hour and 30 minutes by using a cold impact tester, andthen lowering the temperature to −40° C. to cool for one hour and 30minutes, and then further raising the temperature to 140° C., and thenumber of cycles until the molded article generated cracks was measuredto evaluate the resistance to heat shock.

[Pressure Cooker Test]

Pellets to be used were injection-molded to prepare ISO 3167 tensiletest piece under the condition of a resin temperature of 260° C., a moldtemperature of 80° C., an injection time of 15 sec, and a cooling timeof 15 sec, and the tensile strength was measured in accordance with ISO527. After that, by using the pressure cooker tester, the tensile testpiece was exposed to an environment of 121° C. and 100% RH for 50 hours.From the tensile strength before and after the exposure, the tensilestrength retention rate was calculated.

TABLE 1 Examples Comparative Examples 1 2 3 4 5 1 2 3 4 (A) A-1 (partsby weight) 100 100 100 100 100 100 100 100 A-2 (parts by weight) 100 (B)B-1 (parts by weight) 0.4 0.4 0.4 0.4 1.4 B-2 (parts by weight) 0.7 (C)C-1 (parts by weight) 47 47 47 47 46 50 50 50 (D) D-1 (parts by weight)8 8 8 17 D-2 (parts by weight) 8 D-3 (parts by weight) 8 17 D-4 (partsby weight) 8 17 Carbodiimide equivalent/Amount of carboxyl group 1.0 1.01.0 1.0 1.0 1.0 — — — Evaluation Melt viscosity (Pa · s) 205 280 280 270280 240 200 300 280 Resistance to heat shock 360< 300< 300< 300< 300<240 200 240 120 Tensile strength (MPa) 130 132 135 132 130 130 115 118122 Tensile strength retention rate after 50 hr (%) 92 92 90 85 90 70 9081 58

The invention claimed is:
 1. A method of manufacturing an insertinjection-molded article wherein the injected portion thereof is apolybutylene terepththalate composition formed by blending a compositionin the absence of an aromatic polyvalent carboxylic acid esters, thecomposition comprising: 100 parts by weight of a polybutyleneterephthalate resin (A) having 30 meq/kg or less of terminal carboxylgroups with a carbodiimide compound (B) in an amount of 0.8 to 1.2equivalents of the carbodiimide functional group when the amount ofterminal carboxyl groups in the polybutylene terephthalate resin (A) isset as 1, wherein the carbodiimide is selected from the group consistingof di-2,6-dimethylphenyl carbodiimide, poly(4,4′-diphenylmethanecarbodiimide), poly(phenylene carbodiimide), andpoly(triisopropylphenylene carbodiimide); 20 to 100 parts by weight of afibrous filler (C); and 5 to 15 parts by weight of an elastomer (D)selected from the group consisting of styrene-based thermoplasticelastomer, a grafted olefin-based thermoplastic elastomer, a core-shellelastomer composed mainly of an acrylic-based rubber, a polyester-basedthermoplastic elastomer, and mixtures thereof; wherein said compositiondisplays good flowability as evidenced by a melt viscosity of 300 Pa·sor less at a temperature of 260° C. and a shear rate of 1000 sec⁻¹ inaccordance with ISO 11443, and injecting said polybutylene terephthalatecomposition while molten into a mold including a metal insert to form aninsert injection-molded article exhibiting improved resistance to heatshock and wherein (A) and (B) are selected and provided in saidcomposition in concentrations so that 0.5 to 1.5 equivalents ofcarbodiimide functional groups are present per each carboxyl functionalgroup of (A) and wherein (A), (B), (C) and (D) are provided in saidcomposition within the specified ranges so as to facilitate theexpression of said improved resistance to heat shock of said insertinjection-molded article when subjected to 300 cycles of heating at 140°C. for 1.5 hr, and cooling to −40° C. for 1.5 hr., and a tensilestrength retention after 50 hours of 85% to 92% pursuant to ISO 527 at121° C. and 100% relative humidity after 50 hours.
 2. A method ofmanufacturing an insert injection-molded article wherein the injectedportion thereof is a polybutylene terephthalate composition formed byblending a composition comprising: 100 parts by weight of a polybutyleneterephthalate resin (A) having 30 meq/kg or less of terminal carboxylgroups with a carbodiimide compound (B) having a molecular weight of2000 or more in an amount of 0.8 to 1.2 equivalents of the carbodiimidefunctional group when the amount of terminal carboxyl groups in thepolybutylene terephthalate resin (A) is set as 1, wherein thecarbodiimide is selected from the group consisting ofdi-2,6-dimethylphenyl carbodiimide, poly(4,4′-diphenylmethanecarbodiimide), poly(phenylene carbodiimide), andpoly(triisopropylphenylene carbodiimide); 20 to 100 parts by weight of afibrous filler (C); and 5 to 15 parts by weight of an elastomer (D),selected from the group consisting of styrene-based thermoplasticelastomer, a grafted olefin-based thermoplastic elastomer, a core-shellelastomer composed mainly of an acrylic-based rubber, a polyester-basedthermoplastic elastomer, and mixtures thereof; wherein said compositiondisplays good fluidity as evidenced by a melt viscosity of 300 Pa·s orless at a temperature of 260° C. and a shear rate of 1000 sec⁻¹ inaccordance with ISO 11443, and injecting said polybutylene terephthalatecomposition while molten into a mold including a metal insert to form aninsert injection-molded article exhibiting improved resistance to heatshock and wherein (A) and (B) are selected and provided in saidcomposition in concentrations so that 0.5 to 1.5 equivalents ofcarbodiimide functional groups are present per each carboxyl functionalgroup of (A) and wherein (A), (B), (C) and (D) are provided in saidcomposition within the specified ranges so as to facilitate theexpression of said improved resistance to heat shock of said insertinjection-molded article when subjected to 300 cycles of heating at 140°C. for 1.5 hr, and cooling to −40° C. for 1.5 hr., and a tensilestrength retention after 50 hours of 85% to 92% pursuant to ISO 527 at121° C. and 100% relative humidity for 50 hours.
 3. The method ofmanufacturing an insert injection-molded article according to claim 1,wherein the intrinsic viscosity of the polybutylene terephthalate resin(A) of the polybutylene terephthalate resin composition is within therange of 0.67 to 0.90 dL/g.
 4. The method of manufacturing an insertinjection-molded article according to claim 2, wherein the intrinsicviscosity of the polybutylene terephthalate resin (A) of thepolybutylene terephthalate resin composition is within the range of 0.67to 0.90 dL/g.
 5. The method of manufacturing an insert injection-moldedarticle according to claim 1, wherein the tensile strength of theresulting article in accordance with ISO 527 is 120 MPa or more.
 6. Themethod of manufacturing an insert injection-molded article according toclaim 2, wherein the tensile strength of the resulting article inaccordance with ISO 527 is 120 MPa or more.
 7. The method ofmanufacturing an insert injection-molded article according to claim 1,wherein the tensile strength of the resulting article in accordance withISO 527 is 130 MPa or more.
 8. The method of manufacturing an insertinjection-molded article according to claim 2, wherein the tensilestrength of the resulting article in accordance with ISO 527 is 130 MPaor more.